Exemplary embodiments of the invention relate generally to a system and method for suppressing foreign current on railway tracks. Moreover, such exemplary embodiments may relate to suppressing foreign current that can interfere with the proper operation of train detection systems such as grade crossing control systems.
A grade crossing system is generally designed to warn motorists of the presence of an approaching train. Such systems often operate by transmitting and monitoring a discrete electrical current in the rails of the railway track. In many locations, high voltage power lines are routed parallel to, and in close proximity with railway tracks. For various reasons, including inductive coupling, power line energy can find its way onto the track in sufficient levels to interfere with the proper operation of the train detection equipment, especially grade crossing control equipment, causing unintended operation of the warning systems when no train is approaching the crossing.
Currently, either wide band shunts or heavy-duty narrow band shunts are applied between the rails of the track to load the offending current. However, wide band shunts can only be applied outside of the track circuit of the train detection equipment, because they load all frequencies more or less equally. Thus, wide band shunts may be ineffective if the source of the foreign current is close to the grade crossing. Further, when multiple crossings are adjacent to one another wide band shunts cannot be used at all. In some cases, narrow band shunts can have undesirable effects on the operation of the system they are intended to protect. Thus, a train detection system experiencing significant interference from foreign current may have to be replaced or redesigned to operate at a different frequency to avoid the effects of the foreign track current. Such redesigns may be expensive, and in high crossing density locations, the redesign may cause other undesirable results to adjacent crossings. Accordingly, an improved technique for mitigating foreign track current may be desirable.